1. Field of the Invention
The present invention relates to a pulverized toner, an image-forming apparatus for one-component developer and a process cartridge using the pulverized toner.
2. Description of the Related Art
In an oilless pulverized toner, wax is contained in the toner base particles, so that the interface of the pulverized toner tends to be generated where the wax exist. Thus, in general the oilless pulverized toner is easily affected by heat or stress, particularly the oilless pulverized toner is easily affected by the process using heat or applying stress in one-component developing process which is characterized by compact form.
In general, the polymerization toner encapsulating wax is used to ensure the resistance against heat or stress. The polymerization toner is characterized by uniformity of the particle size, and high circularity, thus, it is easy to achieve high image quality and lower production cost. On the other hand, the polymerization toner is inferior in cleaning ability. Thus, in a case of the toner produced by the conventional pulverization process, the pressing force applied to a surface of a photoconductor by an elastic blade is not enough to block the residual toner from passing through the blade, and much larger pressing force is necessary. With regard to the means for keeping the stable cleaning effect, there is a tendency that the friction coefficient of the electrophotographic photoconductor is decreased to improve the releasing ability of the toner with respect to the surface of the photoconductor, and many methods of incorporating a lubricant in a surface layer and a protective layer of an electrophotographic photoconductor are proposed. Examples of the lubricants include a fluorine resin such as polytetrafluoroethylene; resin powders such as a substantially spherical acrylic resin, and polyethylene resin; metallic oxide powders such as silicon oxide, and aluminum oxide. The means for decreasing the friction coefficient of the photoconductor at early stage has been put into practical use; for example, a coating mechanism is placed near the contact part of an elastic blade with a photoconductor to coat a toner or a lubricant, and a lubricant layer is disposed on the surface of the photoconductor. In addition, for the combined blade material, the blade material having relatively low impact resilience is likely to be used in order that the contact part with a photoconductor suppresses the vibration generated by the frictional force between the contact part and the photoconductor thereby to prevent the change of toner blocking property, noise, and fluttering sound.
However, it has been confirmed that the toner produced by adding a releasing component in the toner base particles beforehand to improve the releasing ability when fixing is likely to have higher adhesive force. Therefore, it is difficult to discharge a residual toner, which accumulates easily, after a visible image is formed on the photoconductor in a developing unit and transferred in a transferring unit, and then the residual toner on the photoconductor is blocked at the contact part of the cleaning blade with the photoconductor.
When the toner accumulation is increased at the contact part of the cleaning blade with the photoconductor, the pressing force of the toner partly exceeds blocking force of the blade, and then the toner passes through the contact part of the cleaning blade with the photoconductor. Thus, the problem of the inferior cleaning ability is frequently occurred.
Japanese Patent Application Laid-Open (JP-A) No. 2004-109602 discloses the toner in which the relation of the adhesive stress at 25° C. and 50° C. are defined. The toner is produced by salting out/fusion bonding resin particles and colorant particles in an aqueous medium, not by the melt-kneading pulverization.
Japanese Patent Application Laid-Open (JP-A) No. 2002-169326 discloses the toner in which the relation of the amount of the external additive to the toner particle diameter, and the relation of the adhesive stress to the compressive force are defined. The oilless pulverized toner needs more amount of the external additive to coat the surface of the toner. In the definition of the relation of the change to the compressive force, the exudation of the releasing agent at high temperature and high pressure, which is the inherent problem of the oilless pulverized toner, can not be improved.
Japanese Patent Application Laid-Open (JP-A) No. 2000-3063 discloses the spherical toner having the relative high-circularity of 0.960 or more, however, the adhesive stress relative to the temperature is not defined. Thus, the exudation of the releasing agent at high temperature and high pressure, which is the inherent problem of the oilless pulverized toner, can not be improved.
Japanese Patent Application Laid-Open (JP-A) No. 11-295928 discloses the toner in which the adhesive force among toners and the softening point of the binder resin at a room temperature is defined, however, the adhesive stress relative to the temperature is not defined. Thus, the exudation of the releasing agent at high temperature and high pressure, which is the inherent problem of the oilless pulverized toner, can not be improved.